Lubricating oil composition



United States Patent C) "ice UBRICATING OIL COB/[POSITION Joseph Arthur Verdol, Dalton, 111., assignorto Sinclair Refining-Company, New York, N.Y. a corporation of Maine No Drawing. Filed Aug. 7, 19 57, Ser. No. 676,720

4 Claims. (Cl. 252-515) This invention relates 'to a new class of compounds which are useful as dispersants in hydrocarbon oils. More particularly, this invention relates to compounds of the polyester type formed by reacting a dibasic acid with an alkyl substituted diethanolamine, said polyesters finding particular utility as low temperature dispersants in mineral oils of lubricatingviscosity.

The use of metallic detergents in internal combustion engine lubricating oil compositions is well known, particular utility for these detergents being found in lubricating oil compositions which are subjected to heavy duty service resulting in the oxidation of the oil with the resultant formation of sludges and varnishes. Although the metallic detergents such as metallic petroleum sulfonates have been very useful in maintaining these sludge and varnish formations suspended in the oil they have the disadvantage of being themselves subject to breakdown and deterioration resulting in the formation of a metallic ash which accumulates in the combustion chamber. Nor have these metallic detergents proven effective in dispersing the blow-by contamination of the lubricating oil when the engine is operated in light service and at low operating temperatures. When the engine is cold the cylinder walls act as a condenser for the fuel vapors and combustion products in the cylinder. These contaminants wash past or blow-by thepiston rings into the crank case wherein they tend to emulsify and coagulate causing insoluble sludge deposits which the usual metallic detergents are unable to redisperse. To overcome these blow-by contaminantsand to disperse the sludge deposits in the crank case, attempts have been made to provide ashless dispersants which will prove eifective at the low operating temperatures found in light service internal combustion engines. In accordance with the present invention, the dispersion of the low temperature sludge deposits can be attained by providing in the mineral lubricating oil base a small .but efiective ,amount of the liquid reaction product obtained by reacting approximately equal molar portions of a dibasic acid or an anhydride or ester thereof with an alkyl diethanolamine. The nitrogen-containing polyester thus formed can be added to the lubricating oil base in an amount suflicient to achieve the desired sludge dispersant properties. Generally, the polyester should be added to the base oil in amounts to give about 0.1 to 5 percent or more by weight on the base oil, and preferably, the polyester should be about .75 to 1.5 percent by weight of the base lubricating oil.

The dibasic acids which can be utilized in forming the polyesters ofthe present invention conform to the following general structural formula:

wherein R is a divalent, non-aromatic hydrocarbon radical straight or branched, saturated or unsaturated, con taining 12 to 3 8 carbon atoms. By the term nonaromatic in nature, I mean to include not only aliphatic hydrocarbon acids but also those acids which are nor- "2,944,025 'jPatented July ,5, 1 960 mally monobasic in nature but have been. converted to dibasic acids by the cyclization of their hydrocarbon group as well as cyclic naphthenic dibasic acids. Examples of suitable acids are dodecenylsuccinic, octadecylsuccinic, dimerized unsaturated fatty acids, such as linoleic, ricinoleic, etc. For the purposes of forming the superior low temperature dispersant, however, it is preferred that the dibasic acid be a branched one such as dimerized linoleic acid or dodecenylsuccinic acid. Not only are the dibasic acids useful but also their anhydrides and esters can be employed.

The alkyl substituted diethanolamines useful in preparing the polyesters of the present invention are those .in which the alkyl substituent (R) contains from about 4 to 20 carbon atoms. Preferably the alkyl group is straight chained. Examples of useful alkyl diethanol amines can be enumerated as follows: butyldiethanolamine, octyldiethanolamine, dodecyldiethanolamine, octadecyldiethanolamine, etc.

The polyesters of this invention can be prepared by either of two general methods, i.e. they can be prepared by direct esterification of the dibasic acid or anhydride with the diethanolamine or a dibasic acid ester can be prepared by any of the recognized procedures and the desired polyester prepared by ester interchange between the acid ester and the diethanolamine. The preparations of polyesters found particularly advantageous for use as low temperature dispersants in mineral lubricating oils by each ofthese two methods are illustrated in the EXAMPLE I Preparation of polyester by direct esterificati0n=-A mixture of 79.8 grams of dodecenylsuccinic anhydride (0.30 mole) and 91.5 grams of dodecyldiethanolamine (0.30 mole) was placed in a 300 ml. -4-neck ed flask equipped with a Claisen head, condenser, thermometer and. gas inlet tube through which nitrogen was bubbled during the reaction period. Approximately 0.2 gram of zinc stearate was added to the flask as a catalyst. The flask was heated under atmospheric pressure for about three hours at about ZOO-210 C. whereupon 4 mls. of, water was collected. The reaction mixture was subsequently heated to 200 C. in vacuum under about 610 mm. of pressure for an additional 21 hours. The resultant product was a straw-colored, viscous polymer having the following properties:

Acid No. pH .11 .85 Base No. pH 4 68.00 Nitrogen percent 2.63 (theory 2.6)

A similar polyester is obtained by replacing the dodecyldiethanol Withoctadecyldiethanol or butyldiethanol in an equal molar amount and the products have acid numbers of less than 1.

EXAMPLE I=I Preparation of a polyester by ester interchange- A mixture of 336 grams of the'butyl ester of dimerized linoleic acid (about 2 double bonds per molecule) and 80.5 grams of butyldiethanolamine was placed in a. 500 4-necked flask equipped as described in Example I. 4.16 grams of tetraisopropyl titanate {an estor interchange catalyst) was added to the flask. The mixture was heated under atmospheric pressure in a stream of nitrogen at about 200 C. until 65 grams of butyl alcohol was collected. The reaction product was subsequently heated in vacuum for 16 hours at 200 C. The resultant product was a very viscous, amber-colored polymer showing the following properties:

Acid no 0.0 Nitrogen (basic) percent 2.02

It is believed that the above reactions yield polyesters conforming to the following general formula:

wherein R is as described above, R is the alkyl group of the diethanolamine described above and y is an integer or 1 up to the limit of compatibility of the polyester with the mineral lubricating oil, and preferably, y should be about 5 to 100. Compatibility is used to mean soluble, miscible or otherwise dispersible in the mineral oil without continued agitation and in the amounts required to impart the desired properties to the base oil. Also, in the polyesters R and R should have a total number of carbon atoms of about 22 to 44, preferably more than 30.

The following reactants were polymerized in accordance with the procedures outlined above to obtain polyesters.

The polyesters thus prepared were blended in a solvent-treated Mid-Continent neutral mineral oil having a viscosity of 160 SUS at 100 C. The dispersing ability of the oil-soluble polyesters was studied by diluting 50 mls. of the above mineral oil with 50 rnls. of kerosene and adding to the blend about 1.0 percent by weight of the additive to be tested. To this blend was added 0.5 grams of carbon black (Benny & Smith carbon black, 24 micron size, pH 3.2). The resultant mixture was homogenized three times through a manually operated homogenizer. The mixture was then heated to about 150 C. and cooled to room temperature. One sample contained no additive and another sample contained 1.0 percent by weight of Du Pont LOA 564, a recognized ashless detergent. The ratings for the carbon black suspension test were made visually with the aid of an optical microscope. The suspension tests were conducted on both dry and wet carbon dispersions. For the wet carbon test, 1 percent by weight water was added by homogenization to the mixture. A summary of these tests is presented in Table II following. The additive numbers correspond to those of Table I.

Table II As can be seen from an examination of this table, the better dispersants are formed from the compounds wherein the total carbon atoms in R+R' is from 22 to 44 and R has at least 12 carbon atoms. For example, the additive prepared from sebacic acid and octadecyldiethanolamine was not as effective in dispersing and suspending the carbon black as additives 1, 2 and 4 of this invention. Similarly, additive 3 showed significantly poorer characteristics.

Additives Nos. 2 and 4 were 'further screened as detergents by conducting suspension tests on the sludge deposits which were collected from the oil pan of a Chevrolet engine which had been run under FL-2 conditions. The lubricating oil composition comprised a solventtreated Mid-Continent neutral lubricating oil having a viscosity of 160 SUS at 100 F. and about 0.7 percent zinc dithiophosphate anti-oxidant. The deposits thus collected were washed several times with pentane by decantation and dried on a suction filter. The thus dried sludge was ground to a fine powder. A 10 percent benzene dispersion of the deposits was prepared by blending 50 girls. of the ground deposit in 50 gms. of benzene and homogenized several times. The sludge suspension tests were carried out by dissolving 1.0 percent by weight of the additives to be tested in 5 mls. of solvent-treated Mid- Continent neutral lubricating oil having a viscosity of 160 SUS at 100 'F. and 5 mls. of kerosene. Two mls. of the above-formed sludge dispersion was then placed in the mixture. After boiling oit the benzene, the samples were placed in test tubes and permitted to stand several weeks at room temperature. One of the thus prepared samples contained no additive and another contained Du Pout LOA 564 as a standard of comparison. The amount of agglomerated material was estimated visually with the assistance of an optical microscope and by an inspection of the settling rates.

In the test sample wherein no additive was used the sludge agglomerated and settled to the bottom almost immediately in the form of a hard cake which was impossible to redisperse by shaking the test tube. The polyesters Nos. 2 and 4 which were effective in the suspension of the carbon black were also found to be just as effective in suspending and dispersing the sludge deposits. Although the sludge settled to the bottom of the test tubes having these additives and Du Pont LOA 564, respectively, it could be readily redispersed by shaking the test tubes.

In order to evaluate the additives under actual operating condition several blends were and tested under FL-2 Chevrolet engine conditions. These blends were comprised of the following:

(a) Mid-Continent VI neutral lubricating oil having a viscosity of 160 SUS at F. plus about 0.7 percent zinc dithiophosphate.

(1)) Composition (a) plus 1.0 percent additive No. 1.

(0) Composition (a) plus 1.5 percent additive No. 2.

Carbon Black Suspension Tests on Various Detergents Detergent Additive No.

Results Nnnn 1% (active ingredient) du Pont LOA 564 Additive No. 1

almost immediately.

several Weeks.

7 detergent LOA 564. Additive No. 2

Additive No. a

Additive N0. 4

Additive N O. 5

for only two days.

Carbon black formed large agglomerates which settled out of oil-kerosene mixture Microscopic examination This additive was an excellent dispersant and appeared to disperse wet or dry carbon black equally as good as du Pont L0 64. This additive was a poor dispersant and maintained carbon black in suspension Tests showed this additive to be as good as du Pont LOA 564. Both wet and dry carbon black dispersion containing this additive began to form agglomerates immediately. After one week no carbon black remained suspended.

I 302OR) (d) Composition (a) plus 1.2percent additive similar to No. 4 except prepared from 'dimerized linoleic acid with about, one double bond per molecule (Empol An {SAE 10Wj-30 oil containing basic barium ma- "hogany sulrtonate detergent, zinc dithiophosphate antioxidant, sulfurized sperm oil anti-wear agent, dime'thyl sihcone polymer anti-foaming agent, and Acryloid 763 (a 40 percent concentrate in mineral oil of methacrylate ester polymer in which ester groups are derived from a mixture of alcohols in the C to C range).

(1) Composition (d) plus 1.2 percent additive No. 2.v

A summary of the engine cleanliness ratings of the above blends is presented in Table III below.

wherein R is a non aromaticdivalent hydrocarbon radi cal containing 12'to-38' carbon atoms, R" is an alkyl in an amountoi about 0.1 to 5.0 percent by weight, said I A I polyester being characterized bythe formula: R,

wherein R is a non-aromatic divalent hydrocarbon radi- Piston Oil Oil Push Push Timing Rocker Rocker Top Total Blend Skirt Control Pan Rod Rod Gear Arm Arms Screen Deck Rating Average R ng Chamber Cover Cover Cover,

The results of these tests indicate that the polyester additives which were effective in the carbon black and sludge suspension tests effectively promote engine cleanliness when the engine is operated under light service conditions. For example, comparing test (a) with (b), (c) and (d), it is seen that the additives promoted the overall engine cleanliness although it was also found that du Pont LOA 564 gave a better rating than additives Nos. 1 and 2. When a metallic detergent is present (test [0]), the addition of polyester No. 2 to the blend (test [f]) promoted the low temperature dispersing prop erties of the lubricating oil.

The lubricating oil base stock used as the major portion in the composition of this invention can be any mineral oil of lubricating viscosity. Frequently, the viscosity of such oils will be from about 50 SUS at 100 F. to 500 SUS at 100 F. If desired, the additives of this invention can be prepared in a small amount of the mineral oil base and stored as a concentrate which can later be blended in the desired portions with the final lubricating oil composition or the additive can be formed and added directly to the lubricating oil. In addition to the polyesters of the present inventionother agents can be added to the final composition as desired, for example, pour depressors, VI iinprovers, other dispersants, anti-oxidants, foam preventers, anti-corrosive agents, etc.- Not only do the polyesters of my invention improve the low temperature dispersant properties of mineral lubricating oils as pointed out above but they are also efiective in improving the pour point of the base oil and in raising the viscosity index. Also, the polyester No. 2 of this invention acts as a stabilizer and sludge dispersant in petroleum fuel oils.

It isclaimed: v

1. A lubricating oil composition consisting essentially of a major portion of a mineral oil of lubricating visin an amount suificient to impart sludge-dispersing properties to the lubricating oil composition, said polyester being characterized by the formula:

polyester.

cosity and a polyester compatible with said mineral oil cal containing 12 to 38 carbon atoms, R is an alkyl radical containing 4 to 20 carbon atoms, R and R' contain a total of 22 to 44 carbon atoms and y is from 1 to an integer providing the mineral lubricating oil-compatible polyester.

3. A lubricating oil composition consisting essentially of a major portion of a mineral oil of lubricating viscosity and a polyester compatible with said mineral oil in an amount of about 0.1 to 5.0 percent by weight, said polyester being characterized by the formula:

o 0 R noai-n-r'i-o-omom- ""CHQCHBO) H wherein R is the hydrocarbon portion of dodecylsuccim'c acid, R is an octadecyl radical and y is from 1 to an integer providing the mineral lubricating oil-compatible polyester.

4. A lubricating oil composition consisting essentially of a major portion of a mineral oil of lubricating viscosity and a polyester compatible with mineral oil in an amount of about 0.1 to 5.0 percent by weight, said polyester being characterized by the formula:

wherein R is the hydrocarbon portion of dimerized' linoleic acid, R' is a .butyl radical and y is from 1 to an integer providing the minerallubricating oil-compatible References Cited in the file of this patent UNITED STATES PATENTS 2,094,608 Kritchevsky -r Oct. 5, 1937 2,173,448 Katzman et al. Sept. 19, 1939 2,439,074 Caldwell Apr. 6, 1948 2,494,875 'Hirt Jan. 17, 1950 2,638,449 White et 'al May 12, 1953 2,759,894 Matuszak Aug. 21, 1956 2,764,551 Smith et a1. Sept. 25, 1956 2,805,201 Fischer Sept. 3, 1957 2,831,813 Matuszak et al. Apr. 22, 1958 

1. A LUBRICATING OIL COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR PORTION OF A MINERAL OIL OF LUBRICATING VISCOSITY AND A POLYESTER COMPATIBLE WITH SAID MINERAL OIL IN AN AMOUNT SUFFICIENT TO IMPART SLUDGE-DISPERSING PROPERTIES TO THE LUBRICATING OIL COMPOSITION, SAID POLYESTER BEING CHARACTERIZED BY THE FORMULA: 